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1129 Final Review > Radiation Biology > Flashcards

Radiation Biology Flashcards

1
Q

What is radiation biology and why is it relevant to radiation protection?

A

Radiation biology is the study of the effects of ionizing radiation on living systems. It is relevant to radiation protection because it helps understand how ionizing radiation causes damage and the measures needed to mitigate its effects on biological tissues.

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2
Q

What does radiation biology include?

A

Sequence of events occuring after irradiation, action of the living system to make up for the irradiation and injuries produced as a result of the irradiation

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3
Q

What types of experiments and observations contribute to our understanding of radiation biology?

A

Experiments on animals and plants, as well as observations of humans exposed to radiation (e.g., radiologists, nuclear workers, survivors of atomic bombs), provide valuable insights.

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4
Q

How does ionizing radiation damage living systems?

A

Ionizes atoms that comprize the molecular structure of theses systems

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5
Q

What types of radiation can produce biologic damage through ionization?

A

Types include X-rays, gamma rays, alpha particles, beta particles, and protons.

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6
Q

What are 3 important concepts to help understand the way IR causes injury?

A

Linear energy transfer (LET), Relative biologic effectiveness (RBE) and oxygen enhancement ratio

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7
Q

How is Linear Energy Transfer (LET) defined and measured?

A

LET is defined as the average energy deposited per unit length of track by ionizing radiation, measured in keV/μm.

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8
Q

What are the two types of LET?

A

High LET and Low LET

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9
Q

How is Low LET radiation described?

A

Has high penetration ability, so there is less energy deposited per unit length as the beam travels through the tissue

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10
Q

How is High LET radiation described?

A

Has low penetration ability, so there is more energy deposisted per unit length as the beam travels through the tissue

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11
Q

Which radiation is classified as Low LET?

A

X-ray and Gamma rays

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12
Q

What radiation is classified as High LET?

A

Alpha particles, Ions of heavy nuclei, charged particles relesaed from interactions between neutrons and atoms and low energy neutrons

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13
Q

Why do alpha particles have a higher LET compared to x-ray and gamma rays?

A

Alpha particles have a higher LET because they are charged and deposit energy over a shorter distance as they travel through matter, initiating more ionization events.

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14
Q

What is relative biologic effectiveness (RBE)?

A

Describes the comparative capabilities of radiation with differing LETs to produce a particular biologic reaction

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15
Q

How is RBE calculated?

A

By the ratio of of the type of radiation used is the ratio of the dose of a reference radiation (conventionally 250-kVp x-rays) to the dose of radiation of the type in question that is necessary to produce the same biologic reaction in a given experiment

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16
Q

What is the RBE for x-ray and gamma rays?

A

Approximately 1

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17
Q

What is the RBE for alpha radiation and orther large particle beams?

A

Approximately 3

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18
Q

What is RBE influenced by?

A

The manner in which the dose was delivered

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19
Q

If a dose is delivered over a long period of time how does that impact the effect?

A

The effect is less becomes some cells recover from the damage as time passes

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20
Q

In RBE what are the two ways in which ionizing radiation dose can be stretched?

A

Fractionation and Protraction

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21
Q

Explain what happens during the protraction of a radiation dose.

A

Protraction involves delivering a radiation dose continuously at a low rate over a long period, minimizing damage by allowing cellular repair mechanisms to act.

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22
Q

How do LET and RBE vary between different types of radiation?

A

High LET radiation (e.g., alpha particles) is more damaging, leading to higher RBE, compared to low LET radiation (e.g., X-rays) that causes damage over a longer range.

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23
Q

Define oxygen enhancement ratio (OER) and explain its significance in radiation biology.

A

OER is the ratio of radiation doses required to achieve a specific biological response under anoxic vs. oxygenated conditions. It is significant because oxygen presence enhances radiation effects, increasing tissue radiosensitivity.

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24
Q

What is the OER of xrays and gamma rays?

A

Approximately 3.0 when radiation doses are higher

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25
What is OER when radiation doses are below 2 Gy?
Approximately 2.0
26
What is the OER formula?
Radiation dose without O2/radiation dose with O2
27
In living systems, what levels can biologic damage be observed on?
Molecular, Cellular and Organic
28
Where does damage at the cellular or organic level always start?
At the molecular level
29
In what ways can exposure to ionizing radiation alter human cells?
Can disturb the cell's chemical balance and the way it operates so it can no longer perform its normal tasks
30
What is the impact of a sufficient quantity of somatic cells being affected by ionizing radiation?
Entire body processes may be disrupted
31
What happens if radiation damages the germ cells?
The damage may be passed on to future generations in the form of genetic mutations
32
What are the two classifications of ionizing radiation interaction on a cell?
Direct action and indirect action
33
What does direct action involve?
When ionizing particles directly interact with vital biologic macromolecures (DNA, RNA, Proteins and Enzymes)
34
What does indirect action involve?
When ionizing particles directly interact with H20, which produces free radicals that then interact with DNA
35
Which radiation action is more likely in the body?
Indirect action since the body is composed of around 80% of water so the probability with it is higher
36
What is radiolysis?
The dissociation of molecules by ionizing radiation
37
How does the radiolysis of water occur?
When x-ray photons interact with water molecules which results in their separation into other molecular components
38
When x-rays photons interact with water what do they produced?
H2O molecule breaks down into ions and free radicals
39
What happens to the ions?
They can recombine to form a water molecular and can no biologic damage
40
What happens to the free radiaclas?
They migrate to abother molecure, like DNA, and destructively interact with it by ionizing or rupturing chemical bonds
41
What does the interaction between the free radiacals and DNA produce?
A molecular or point lesion in the DNA
42
How else can free radicals spread biologic damage?
By combining with other molecule to form toxic substances that migrate to DNA
43
What are the 5 specific effects of ionizing radiation on DNA?
Single strand breaks, Double strand breaks, Double strand breaks in the same rung, Mutations and Covalent cross links
44
What is a single strand break?
Ionizing radiation interacts with DNA macromolecule, transfers energy, and ruptures one of the molecule’s chemical bonds possibly severing one of the sugar-phosphate chain side rails
45
What is the rupture in a single strand break called?
Point mutation
46
What is capable of repairin the damage of single strand breaks?
Repair enzymes
47
What is a double strand break?
Additional breaks in the sugar phosphate molecular chain cause by further exposure to the affected DNA
48
How does repair of double strand breaks compare to single strand?
More difficult and not as easily repaired
49
If repair does not occur in a double strand break what happens?
Further separation can occur in the DNA chain threatening the life of the cell
50
When are double strand breaks more likely to occur?
With densly ionizing radiation (High LET radiation)
51
What is a double strand break in the same rung?
When two interactions hit each of the two sugar phospate chains within the same rung of the DNA ladder
52
What is the result of a double strand break in the same rung?
A cleaved or broken chromosome, which contain an unequal amount of genetic material
53
What happens if the damage chromosomes of a double strand break divide?
The daughter cell will receive an incorrect amount of genetic material, which will culminate in the death or impaired function of the daughter cell
54
What is a mutation?
When there is a loss of or change in the nitrogenous base on the DNA chain as a result of interactions with IR
55
What is the direct consequence of mutational damage to DNA?
An alteration in the base sequence, which is known as a mutation
56
If the mutation cannot be reversed what is the impact?
Incorrect genetic information will be transferred to one of the two daughter cells when the cell divides
57
What are covalent cross links?
Chemical unions created between atoms by the single sharing of one or more pairs of electrons
58
What are covalent cross linkes initiated by?
High-LET radiation
59
How do the covalent cross links form?
After irradiation, some molecules become sticky which then attach to other macromolecules or segments of the same macromolecule chain
60
What are the two patterns of covalent cross links?
Intrastrand cross links and interstrand cross links
61
What are intrastrand cross links?
When the molecules form the cross links by sticking to two portions of the same DNA strand
62
What are interstrand cross links?
When the molecules form the cross links by sticking to complementary DNA strands
63
What other radiation induced changes are just as serious as DNA damage?
Large scale structural changes in chromosomes
64
Where are radiation-induced chromosome breaks revealed?
During the metaphase and anaphase of cell division, when the length of the choromosome is visible
65
What are chromosomal fragments?
Fragments that are produced after chromosome breakage
66
What are features of chromosomal fragments?
They are very active and have a strong tendency to adhere or combine to similar ends
67
What are some things chromosomal fragments do?
Rejoin their original configurations Fail to rejoin and create aberrations Join other broken fragments to create new chromosomes
68
What are two types of chromosomal anomalies that are observed in metaphase?
Chromosome abberattions and Chromatid aberrations
69
When do chromosomal aberrations occur?
When irrations occurs in early interphase before DNA synthesis
70
What happens as a result of chromosomal aberrations?
The daughter cells generated as part of cell division inherit the damage
71
When do chromatid aberrations occur?
When interactions occur in later interphase after DNA synthesis
72
What happens as a result of chromatid aberration?
Only one daughter cell is affected
73
What are the consequences to the cell from structural changes within the nucleus?
Restitutions, Deletion, Broken-end arrangement, and Broken-end arrangement without visible damage
74
What is restitution?
When the break rejoins its original configuration with no visible damage
75
Where is restitution seen the most?
In single-chromosome break mends
76
What is deletion?
Where a part of the chromosome or chromatid is lost at the next cell division which results in a mutation
77
What is a broken cell rearrangement?
When a grossly misshapen chromosome is produced which results in cell mustation
78
What is a broken cell rearrangement without visible damage?
When the chromatid's genetic material has been rearranged but the chromosome appears normal. Which results in cell mutation
79
What is target theory?
The idea that a master, or key molecule that maintains normal cell function is believed to be present in every cell
80
Why is a target theory molecule so important?
Because the molecule is vital to the survival of the cell and is presumed to be the DNA
81
What is the result of key molecule receiving multiple hits from ionizing radiation?
The master molecule may be inactivated
82
What happens is the master molecule is inactivated?
Healthy cell function will cease to exist and the cell will dies
83
How does damage to the cell's nucleus reveal itself?
Instant death Reproductive death Apoptosis (programmed cell death) Mitotic or genetic death Mitotic delay Interference with function
84
What is a cell survival curve?
A classic method of displaying the sensitivity of a particular type of cell to radiation
85
What do cell survival curves demonstrate?
The fraction of surving cells after specific doses of radiation
86
How is Low LET radiation reflected on the cell survival curve?
A shoulder to the curve at lower doses indicates that the cell has some ability to repair damage at low doses
87
How is the High LET radiation reflected on the cell survival curve?
No shoulder is represented, which means that little to no repair takes place
88
What are the bodies radiosensitive cells?
Basal cells of the skin Blood cells like lymphocytes and erythrocytes Intestinal crypt cells Reproductive cells
89
What the bodies radioinsensitive cells?
Brain cells Muscle cells Nerve cells
90
What plays a major role in determining the amount of biologic response is produced in a tissue?
The amount of radiation energy transferred into the tissue (LET)
91
How does LET relate to biologic damage?
As LET increases, the ability of the radiation to cause damage also increases until it reaches a maximum value
92
What does the relationship between LET and radiosensitivity?
LET can incluence radiosensitivity
93
How does oxygen relate to radiosensitivity?
Oxygen enhances the effects of ionizing radiation and increase tissue radiosensitivity
94
When is high oxygen content preferred in tissues?
During radiotherapy to increase the radiosensitivity of tumor
95
What are the Law of Bergonie and Tribondeau?
Basic principles that relate metabolism to radiosensitivity
96
What does the law state?
Radiosensitivity of cells is directly proportional to their reproductive activity and inversely proportional to their degree of differentiation
97
According to the law when do the most pronounced radiation effects occur?
In cells with the least maturity and specialization, cells with the greatest reproductive activity and cells with the longest mitotic phases
98
Which cell types are more sensitive, young or mature?
Young cells, like stem and immature cells
99
Which tissues/organs are more sensitive?
Young developing tissues
100
What are specific biologic factors that affect cell sensitivity?
The presence of oxygen, age of patient, sex of patient and presence of chemical agents
101
How does the presence of oxygen affect cell sensitivity?
The presence of oxygen enhaces sensitivity
102
How does age affect cell sensitivity?
Younger peopler are typically more sensitive, but elderly people are also very radiosentive
103
How does the sex of a patient affect cell sensitivity?
Men are slightly more radiosensitive because their X chromosomes do not have an allele
104
How does the presence of chemical agents affect sensitivity?
Can be protective or sensitizing
105
What chemical agents are protective?
Vitamin A, C and E and some sulfur compounds
106
What chemical agents are sensitizing?
Antibiotics and chemo drugs
107
What are the 3 ways radiation damage presents itself in large molecules, especially proteins?
Main chain scission, cross-linking and point lesions
108
What is main chain scission?
Breakage of the chain
109
What is cross linking?
Adnormal adherence of one part of the molecule to another
110
What are point lesions?
Small changes in chemical bonds
111
How is irradiation of large molecules classified?
No serious, since they're all repairable and even if they're not repaired they are multiple copies
112
What is hematologic depression?
The reduction of the number of active cells in circulation
113
What is a whole body dose that can produce hematologic depression?
Whole body dose of 0.25 Gy
114
What is a depletion of immature blood cells?
When radiation decreases the number of immature blood cells produced in the bone marrow, which ultimately reduces the number of mature blood cells in the blood stream
115
What happens to bone marrow cells if they haven't been destroyed by irradiation?
They can repopulate after a period of recovery, but the time needed for recovery is based on the dose received
116
What are the effects of radiation on red blood cells (erythrocytes)?
They are the radiosensitive cell since they are high in O2, but because they have a short lifespan they're not the most radiosensitive in the blood
117
What can happen to people who receive a whole body dose in excess of 5 Gyt?
They might die in 30-60 days
118
What are the effects of radiation on leukocytes?
they are the most radiosensitive, which can cause the body to lose its ability to combat infection
119
What are the effects of radiation on platelets?
Least radiosensitive of the blood cells
120
What are the effects of radiation on skin cells?
Highly radiosensitive because they have a high reproduction rate
121
What are the effects of radiation on intestinal linign?
Highly radiosensitive
122
Which cells are relatively radioresistant?
Muscle tissue and nerve cells
123
When are nerve cells radiosensitive?
In children since their rapidly maturing
124
What are the effects of radiation on reproductive cells?
Immature speratazoa and ova are extremely radiosensitive

1129 Final Review (6 decks)

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